ORTHO-ARYLATION OF 3,5-DI-TERT-BUTYLPHENOL WITH ARYLLEAD(IV) DERIVATIVES - A FACILE SYNTHESIS OF STERICALLY HINDERED PHENOLS

The reaction of aryllead(IV) triacetates with 3,5-di-tert-butylphenol 1 has been shown to yield very hindered 2-aryl-3,5-di-tert-butylphenols and 2,6-diaryl-3,5-di-tert-butylphenols such as 15 and 16. The mechanism of this arylation reaction with aryllead(IV) derivatives is discussed. A free radical pathway has been excluded. The favoured pathway must involve the occurrence of covalent aryl(aryloxy)lead (IV) diacetate intermediates, although they have not been detected. The required aryl cation behaviour of the lead reagents is supported by C-13 NMR spectroscopic studies on aryllead triacetates.